Diseases Diseases

Common Shrub Diseases

Published at 03/24/2012 15:31:03

Common shrub diseases


Shrubs are different from the trees due to their short height and multiple stems. Shrubs have dense foliage and many small leafy branches that grow close together. In some common garden practice, the shrubs are broad leaved plants that are either evergreen or deciduous. But just like all other plants, the shrubs are prone to many diseases some of which are easy to control and treat. Most of the fungal diseases are caused by the bacteria and the fungi. These organisms enter the body through a wound on the shrub that is caused by mechanical damage or pruning.

Common shrub diseases

There are many types of shrub diseases that are caused by different factors and they manifest in diffrent ways. The following are the common types of shrub diseases.

  • Sooty mold: this is a gray or black fuzzy mold that tends to cover the stem, leaves, flower bud and the fruits of the shrub. It is caused by a fungus that grows on the honey dew that is secreted by the insects during the hot and humid weather.
  • Blights: it is caused by bacteria and it affects the stem, leaves and the flowers. The affected parts feel crispy, the stems bend back to form a shepherd's hook look and turn black or dark brown. These types of shrub diseases occur during the wet and cool conditions.
  • Powdery mildew: it is caused by a fungus that causes dusty and gray patches on the shrubs during the hot and humid seasons. If not treated on time, it can affect the whole stem and leaves resulting to a stunted and distorted growth, early dropping of the leaves and yellowing of the leaves.
  • Root rots: it is caused by the phytophthora fungus that attacks the roots of the shrub to produce brown streaks. The infected shrubs decline slowly and eventually die.
  • Cankers: these are caused by fungi, bacteria or injury. The affected areas are round with raised edges, others ooze some fermented bacteria that cause the slow decline of the shrub and subsequent death.
  • Leaf diseases: these shrub diseases are caused by fungi and bacteria. The affected shrub tends to have circular edges and the leaves are yellow, red or brown. This condition is worse during the humid weather conditions.

Treatment of common shrub diseases

The different types of shrub diseases are treated depending on the cause of the diseases and the symptoms that occur.

  • Sooty mold: it is treated by reducing the excretion of honeydew and sucking insects, use of the good and recommended chemicals that control the sucking insects and the fungus that grows on the honeydew and washing of the infected foliage to help in the dilution of the honeydew as well as wash off the mold.
  • Powdery mildew: it can be treated through use of wettable sulfur spray or other recommended fungicides. The wettable sulfur may injure tender foliage so it is important to be extra careful when using it.
  • Root rot: it is treated by identifying and cuing the specific root disease, proper pruning and fertilization that promotes the trees vigor.
  • Cankers: there are no effective chemicals that can cure cankers. Therefore, cankers can be controlled by removing the affected branches or the whole tree and isolating them from the rest of the plantation to avoid spread of the disease.
  • Leaf diseases: it is treated by the use of fungicides and chemicals that should be used when the diseases are spotted. The instruction should be followed strictly.


  • Sooty mold: since they are prevalent during high temperatures and limited moisture, the plant should be properly watered during the drought season and hot climate.
  • Powdery mildew: it does well in the moist conditions hence moisture should be controlled and the shrub should be pruned to allow effective air movement.
  • Root rot: ii can be prevented by avoiding lower trunk and root damages and soil sterilization with the appropriate pesticides like the vapam and the methyl bromide.
  • Cankers: it is prevented by avoiding wounds on the shrub tree, planting the shrub in some good place that has the right fertilizer quantity.
  • Leaf diseases: prevented by pruning the shrubs and removing all the fallen leaves.